Engine starter gearing



Feb. 12, 1946. J. E. BUXTON 7 2,394,531

' ENGINE STARTER GEARING Filed on. 20, 1944 2 Shee ts-Sheet 1 40ml x Q hWITNESS: /ww 36mm.

A TTORN E Y Feb. 12, 1946. J. E. BUXTON ,5

ENGINE STARTER GEARING Filed Oct. 20, 1944 2 Sheets-Sheet 2 A TTORNEYPatented Feb. 12, 1946 ENGINE STARTER GEARIN G flamestE. 'Buxtom Elmira,N. Y.,- assignor to BendixAviation Corporation, South Bend, Ind., a

corporation of Delaware Application October 20, 1944, Serial No.'559,587

11 Claims.

'The present inventionrelates to engine starters and more particularlyto a drive of. the automatically engaging and disengaging type which isadapted to maintain its engagement until the engine is reliablyself-operative.

It is an object of the'present invention to provide a novel starterdrive of the above type which is efiicient and reliable in operationunder all conditions of use.

It is another object to provide such a device which is completely underthe control of the operator at all times. v

It is another object "to provide such a device in which the armatureshaft of the motor/ s shifted longitudinally to maintain engagement ofthe drive.

It is another object to provide such a device which is so arranged thatthe longitudinal movement of the armature can be accommodated withoutelongation or special construction of the commutator and/or brushes ofthe motor.

'It is a further object to provide such a device in which undesiredengagement of the drive is effectively prevented.

It is another objectto provide such a device in which the disengagementof the drive is effected concurrently with the deenergization of "thestarting system.

Further objects and advantages will be apparent from the followingdescription taken in connection with the accompanying drawings in which:

Fig, 1 is a semi-diagrammatic representation of a starting systemconstituting a preferred embodiment of the invention, the startingmotor, starting switch and drive gearing beingshown in side elevation,partly broken away, and or idle position; and

Fig. 2 is a similar view showing the parts in cranking position.

In Fig. 1 of the drawings there is illustrated a starting motorindicated generally by the numeral I comprising a frame or housing 2 inwhich are mounted the fields 3 in the usual manner, and an armature 4with a commutator :I' mounted on a shaft '5 which is slidably journalledat its ends in bearings 6 and I formed on the ends of the motor frame 2.

According to the present invention spring means are provided fornormally maintaining the armature '4 decentered with respect to thefields 3 of the motor. As here shown this means comprises a thrustmember 8 slidablymounte'd in the motor bearing 6 and urged intoengagement with the end of the armature shaft 5 by a comin normalpression spring 9 retained in said bearing by suitable means such as'acap I0 threaded thereon and provided with a vent opening I I tofacilitate longitudinal movement of the thrust member in the bearing.

Means for restraining the decenteringmeans is providedin the form of -alatch member I2 mounted for radial sliding movement in the thrust member8,a compression'spring I3 being provided to urge the latch member I2 inan upward direction as. shown in'Fig. 1. The bearing 6 is preferablyprovided with a bushing orlining member I4 which bushing is slottedlongitudinally as shown at I5 in-order to receive theprojecting end ofthe latch IZ. Since the bushing I4 is a forced fit in'thebearing 6,theengagement of the latch I2 in the notch I5 preventsrotation of thethrust member 8.

The bearing Sis provided with a'radial opening I6 in communicationwiththe slot I5 of the bushing I 4 and adapted to receivetheend of the latchI2 when it is moved'into registry therewith. When the latch so entersthe opening Hi, the thrust member 8 is retained against longitudinalmovement, the spring 8 being held under compression.

The centered position of the armature 4 is lpreierahly defined by athrust bearing 5which limits the longitudinal movement of the shaft'tothe left in Fig. 2. Brushes 4a are mounted in the motor frame 2 inposition to be centered on the commutator 4 when the armature is in itscentered position. When the armature is in'its decentered position, thebrushes extend slightly beyond the end of the commutator as showninFig.1,-but since the armature iscentered at all times during the rotationthereof under load, it is unnecessary with this constructionto extendthe commutator beyond its normal dimensions.

The endof the armature shaftbwhich projects through the motor bearing Iis extended as shown at I'-' and has a drive head and sleeve I8 fixedthereon in any suitable manner as by means of a cross pin I9 retained bya lock ring 20. A screw shaft 2| is slidably journalled on a reducedcylindrical extension 22 of .the drive head I8 and is yieldablyconnected to rotate with the same by means of a torsion and compressionspring 23 which is connected to the drive head I8 by an the pinion fromthe screw shaft 2i are provided in the form of a nut 28 threaded on thescrew shaft, a barrel 29 fixed to the nut, a dental clutch member 30non-rotatably connected to the barrel as by means of radial lugs 3|projecting into slots 32, and retained therein by means of a thirnble 33having a flange 34, extending into circumferential groove 35 in theinterior of the barrel. The pinion 25 has fixed thereon in any suitablemanner a driven dental clutch member 36 adapted to cooperate with theclutch member 30 and held in proximity thereto by an inwardly extendingflange 3'! of the thimble 33. A compression spring 38 between the twoclutch members 30 and 36 serves to normally maintain their teeth out ofengagement as shown in Fig. 1.

The centering effect of the magnetic flux through the field and armatureof the starting motor when the motor is energized is utilized to assistin moving the pinion 26 into initial engagement with the engine gear 21and to maintain the pinion in such engagement. When the motor is firstenergized, the flux through the field and armature is heavy due to thelack of counter E. M. F. in the armature so that the armature isforcibly centered with respect to the field thus moving the armatureshaft into the position illustrated in Fig. 2. At this time, the latchI2 is brought into registry with the opening 56 in the motor bearing 6whereby the latch holds the thrust member 8 in retracted position andprevents the spring 9 from attempting to decenter the motor armature.

Means under the control of the operator are provided for actuating thelatch I2 so as to release the thrust member 8 when it is desired todemesh the drive pinion. As here shown this is accomplished by mountinga magnetic starting switch 39 on the motor bearing 6 and providing theplunger 40 thereof with an extension 4| which traverses the opening I6and extends to a position where its end enters the slot I5 in thebushing I4 when the switch is in its open position as shown in Fig. 1.When the switch is closed, the extension M of the plunger is retractedas shown in Fig. 2 so as to permit the latch I2 to enter the opening I6.

Means are preferably provided for yieldably holding the armature 4 inits centered position during the starting operation. As here shown thismeans comprises a spring pressed detent 43 mounted in the bearing 6 inposition to enter an annular groove 42 in the end of armature shaft 5when the armature is centered with respect to the motor fields.

In operation, starting With the parts in the positions illustrated inFig. l closure of the starting switch by the operator withdraws theplunger extension M and at the same time energizes the starting motorwhereby the flux traversing the field and armature thereof causes thearmature to be forcibly moved to the left to the position shown in Fig.2, whereupon the latch I2 enters the opening I6, holding the thrustspring 9 compressed, and the detent 43 enters the groove 42 so as toyieldingly retain the armature in its centered position. The initialrotation of the armature shaft 5 is transmitted through the drive headI8, and spring 23 to the screw shaft 2!, whereby the nut 28 on the screwshaft is traversed to the left, moving the pinion ahead of it by virtueof the spring 38, until the pinion engages the stop collar 44 fixed onthe armature shaft. Further movement of the nut 28 forces the clutchmember 30 of the barrel into engagement with the driven clutch member 36of the pinion, after which the pinion is constrained to rotate with thescrew shaft to crank the engine.

As long as the operator maintains the starting switch 39 closed, thethrust member 8 is held by the latch I2, and the armature 4 is kept inits centered position both by the flux traversing the armature andfield, and by the engagement of the detent 43 in the groove 42 of thearmature shaft 5. If the engine should fire during this time, theacceleration of the engine gear 21 will cause the pinion 26 to beaccelerated above the speed of the motor, and the initial accelerationwill be transmitted back through the clutch members 36, 30 to the nut 28causing it to move back on the screw shaft 2|. This movement is notsuflicient to demesh the pinion from the engine gear however but merelyreleases the clutch members 36, 30 and permits the pinion to overrun themotor shaft freely while remaining in partial mesh with the engine gear21.

If the engine should not continue to be self operative, the pinion willslow down whereupon the screw shaft 2| will traverse the nut 28 back tocranking position, and rotation of the engine by the starter drive willbe resumed. In order to insure such traversal of the nut 28, a springwire detent 45 is preferably mounted in the pinion clutch member 36 inposition to spring outwardly and bear frictionally on the interior ofthe thimble 33 which is attached to the barrel 29 so that there isalways a slight frictional connection between the pinion and the barrel.

When the engine has become reliably self operative, the operator willopen the starting switch 39 whereupon the extension II of the switchplunger engages the latch I2 and forces it out of the opening IS in thebearing 5. The spring 9 is thus released so that the energy storedtherein is available to move the thrust member 8 to the right andthereby translate the armature 4 to its decentered or idle position thusdisengaging the pinion from the engine gear.

In connection with the operation of the spring 9 and thrust member 8 ithas been found that the initial centering action of the armature whenthe starting switch is closed is quite energetic. The spring 9 maytherefore be made sufiiciently heavy to insure prompt movement of thearmature to its idle position when the starting motor is deenergized andto insure against any undesired shifting of the starting motor towardoperative position due to accelerational forces of the vehicle on whichthe device may be mounted.

Although but one embodiment of the invention has been shown anddescribed in detail, it will be understood that various changes may bemade in the design and arrangement of the parts without departing fromthe spirit of the invention as defined in the claims appended hereto.

What is claimed is:

1. In an engine starter an electric motor comprising a field and anarmature having a shaft projecting therefrom, a pinion journalled on thearmature shaft having an overrunning connection therewith and movablelongitudinally therewith into and out of mesh with a gear of an engineto be started, spring means normally holding the armature decenteredwith respect to the field to thereby position the pinion out ofengagement with the engine gear, and manually controlled means forrestraining the decentering means.

2. An engine starter as set forth in claim 1 including further means forcontrolling the energization of the starting motor and for concurrentlycontrolling said restraining means.

3. An engine starter as set forth in claim 1 including further a switchfor controlling the energization of the motor, and means responsive tothe closing of said switch for releasing the restraining means.

4. In a starter motor having a longitudinally shiftable armature shaft apinion journalled thereon having an overrunning connection therewith andshiftable thereby into and out of mesh with a gear of an engine to bestarted, a spring means biasing the armature shaft in position to demeshthe pinion, a latch for restraining the spring means and manuallycontrolled means for releasing the latch.

5. An engine starter as set forth in claim 4 including further a detentfor yieldably holding the armature shaft in position to maintain thepinion in mesh with the engine gear.

6. An engine starter as set forth in claim 4 including further a. switchfor controlling the starting motor having a movable plunger adapted toengage and release the latch when the switch is open.

7. In a starter for internal combustion engines a motor having a fieldand an armature with a shaft extending therefrom at both ends, a pinionslidably journalled on one end of the armature shaft, means foractuating the pinion by the shaft including a clutch and a threadedconnection, spring means operating on the opposite end of the shaft tomove the shaft axially to decenter the armature with respect to thefield, a latch for holding said spring means compressed and manuallycontrolled means for releasing the latch.

8. In a starter for internal combustion engines a motor having a fieldand an armature with a shaft extending therefrom at both ends, a pinionslidably journalled on one end of the armature shaft, means foractuating the pinion by the shaft including an overrunning clutch and athreaded connection, spring means operating on the opposite end of theshaft to move the shaft axially to decenter the armature with respect tothe field, a latch for holding said spring means compressed, and meansresponsive to deenergization of the starting motor for releasing thelatch.

9. An engine starter as set forth in claim 8 in which the centering ofthe armature by magnetic flux when the motor is energized is arranged tomove the pinion into partial mesh with a gear of the engine to bestarted, and said threaded connection is arranged upon rotation of thearmature to move the pinion fully into mesh with the engine gear and toclose said clutch.

10. In an engine starter a pinion, electromagnetic means for moving thepinion longitudinally into mesh with a gear of an engine to be startedand for rotating the pinion to thereby crank the engine, spring meansfor resisting the magnetic shifting movement of the pinion therebystoring I up energy therein for shifting the pinion out of mesh with theengine gear, and manually controlled means for restraining the springmeans.

11. In an engine starter a pinion, electromagnetic means for moving thepinion longitudinally into mesh with a gear of an engine to be startedand for rotating the pinion to thereb crank the engine, compressionspring means for resisting the magnetic shifting movement of the pinion,thereb storing up energy in the spring for shifting the pinion out ofmesh with the engine gear, means for holding the spring compressed, andmeans responsive to deenergization of the electromagnetic means, forreleasing the holding means.

JAMES E. BUXTON.

